Anisotropic drapes and systems

ABSTRACT

An anisotropic wound drape for treating a wound on a patient includes a flexible sheet for placing over a tissue site The flexible sheet includes a first isotropic zone, and a second isotropic zone. The first isotropic zone and the second isotropic zone are configured to provide the flexible sheet with anisotropic stretching properties. The anisotropic drape may used as part of a reduced-pressure wound treatment system. Other systems and methods are also presented.

RELATED APPLICATIONS

The present invention is a divisional of U.S. patent application Ser.No. 12/475,231, entitled “Anisotropic Drapes and Systems,” which claimsthe benefit, under 35 USC §119(e), of the filing of U.S. ProvisionalPatent Application Ser. No. 61/057,807, entitled “Reduced-pressureSurgical Wound Treatment System,” filed May 30, 2008; U.S. ProvisionalPatent Application Ser. No. 61/057,798, entitled “Dressing Assembly ForSubcutaneous Wound treatment Using Reduce Pressure,” filed May 30, 2008;U.S. Provisional Patent Application Ser. No. 61/057,808, entitled“See-Through, Reduced-Pressure Dressing,” filed May 30, 2008; U.S.Provisional Patent Application Ser. No. 61/057,802, entitled“Reduced-Pressure Dressing Assembly For Use in Applying a ClosingForce,” filed May 30, 2008; U.S. Provisional Patent Application Ser. No.61/057,803, entitled “Reduced-Pressure, Linear-Wound Treatment System,”filed May 30, 2008; U.S. Provisional Patent Application Ser. No.61/057,800, entitled “Reduced-Pressure, Compression System and Apparatusfor use on a Curved Body Part,” filed, May 30, 2008; U.S. ProvisionalPatent Application Ser. No. 61/057,797, entitled “Reduced-Pressure,Compression System and Apparatus for use on Breast Tissue,” filed May30, 2008; U.S. Provisional Patent Application Ser. No. 61/057,805,entitled “Super-Absorbent, Reduced-Pressure Wound Dressing and System,”filed May 30, 2008; U.S. Provisional Patent Application Ser. No.61/057,810, entitled “Reduced-Pressure, Compression System and Apparatusfor use on a Joint,” filed May 30, 2008; U.S. Provisional PatentApplication Ser. No. 61/121,362, entitled “Reduced-Pressure Woundtreatment System Employing an Anisotropic Drape,” filed Dec. 10, 2008;and U.S. Provisional Patent Application Ser. No. 61/144,067, entitled“Reduced-Pressure, Compression System and Apparatus for use on a Joint,”filed Jan. 12, 2009. All of these provisional applications areincorporated herein by reference for all purposes.

BACKGROUND

The present invention relates generally to medical treatment systems,and more particularly, to anisotropic drapes and reduced-pressure woundtreatment systems and methods employing anisotropic drapes.

Vapor and oxygen permeable isotropic film dressings, frequently calleddrapes, may be used to cover wounds, or damaged areas of tissue, tofacilitate healing and prevent infection. The elasticity of theseisotropic drapes is substantially uniform. This can be a problem,however, if one would like to regulate translation or approximation oftissue, such as dermal tissue or subdermal tissue, at a specific rate inone direction and at another rate in another direction. Improperregulation of tissue translation may involve negative side-effects,including, but not limited to, blisters, hyper-pigmentation, as well asmany other skin complications and irritations. Other shortcomings mayexist as well

BRIEF SUMMARY

Shortcomings with wound care systems and methods are addressed by theillustrative embodiments as shown and described. According to oneillustrative embodiment, a reduced-pressure wound treatment system fortreating a tissue site on a patient includes a wound drape that has aflexible sheet with a first isotropic zone and a second isotropic zone.The first isotropic zone and the second isotropic zone are configured toprovide the flexible sheet with anisotropic stretching properties. Thesystem also includes a manifold for disposing between the wound drapeand the tissue site and a reduced-pressure subsystem for delivering areduced pressure to the manifold.

According to another illustrative embodiment, a wound drape includes aflexible sheet for placing over a tissue site. The flexible sheet has afirst isotropic zone and a second isotropic zone. The first isotropiczone and the second isotropic zone are configured to provide theflexible sheet with anisotropic stretching properties.

According to another illustrative embodiment, a wound drape includes aflexible sheet and an anisotropic member coupled to the flexible sheet.The flexible sheet and anisotropic member are configured to provide theflexible sheet with anisotropic stretching properties such that theflexible sheet stretches more in a first direction than in a seconddirection.

According to another illustrative embodiment, a wound drape includes aflexible sheet and a fluidly inflatable bladder coupled to the flexiblesheet. The flexible sheet and fluidly inflatable bladder are configuredto provide the flexible sheet with anisotropic stretching propertiessuch that the flexible sheet stretches more in a first direction than ina second direction. The inflatable bladder may take numerous forms. Thewound drape may provide a closing force.

According to another illustrative embodiment, a method for treating atissue site on a patient with reduced pressure includes disposing amanifold proximate the tissue site, disposing an anisotropic wound drapeover the manifold, sealing the anisotropic drape to the patient'sepidermis, and fluidly coupling a reduced-pressure source to themanifold. The anisotropic drape includes at least a first isotropic zoneand a second isotropic zone such that the anisotropic drape stretchesmore in a first direction than a second direction.

According to another illustrative embodiment, a method of manufacturinga wound drape includes the step of forming a flexible sheet for placingover a tissue site with a first isotropic zone and a second isotropiczone. The first isotropic zone and the second isotropic zone areconfigured to provide the flexible sheet with anisotropic stretchingproperties.

Other features and advantages of the illustrative embodiments willbecome apparent with reference to the drawings and detailed descriptionthat follow.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be obtainedby reference to the following Detailed Description when taken inconjunction with the accompanying Drawings wherein:

FIG. 1 is a schematic, perspective view with a portion shown incross-section of an illustrative embodiment of a reduced-pressure woundtreatment system;

FIG. 2 is a schematic, cross-sectional view of a portion of thereduced-pressure wound treatment system of FIG. 1;

FIG. 3A is a schematic, cross-sectional view of a first isotropic zoneand a second isotropic zone of an illustrative embodiment of a wounddrape;

FIG. 3B is a schematic, cross-sectional view of a first isotropic zoneof another illustrative embodiment of a wound drape;

FIG. 4A is a schematic, top view of an illustrative embodiment of aportion of a reduced-pressure wound treatment system;

FIG. 4B is a schematic, cross-sectional view of the reduced-pressurewound treatment system of FIG. 4A taken along line 4B-4B in FIG. 4A;

FIG. 5A is a schematic, top view of an illustrative embodiment of aportion of a reduced-pressure wound treatment system;

FIG. 5B is a schematic, cross-sectional view of the reduced-pressurewound treatment system of FIG. 5A taken along line 5B-5B in FIG. 5A;

FIG. 6A is a schematic, top view of an illustrative embodiment of aportion of a reduced-pressure wound treatment system;

FIG. 6B is a schematic, cross-sectional view of the reduced-pressurewound treatment system of FIG. 6A taken along line 6B-6B in FIG. 6A;

FIG. 7A is a schematic, top view of an illustrative embodiment of areduced-pressure wound treatment system; and

FIG. 7B is a schematic, cross-sectional view of the reduced-pressurewound treatment system of FIG. 7A taken along line 7B-7B in FIG. 7A.

DETAILED DESCRIPTION

In the following detailed description of the illustrative embodiments,reference is made to the accompanying drawings that form a part hereof,and in which is shown, by way of illustration, specific embodiments inwhich the invention may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention, and it is understood that other embodiments may be utilizedand that logical structural, mechanical, electrical, and chemicalchanges may be made without departing from the spirit or scope of theinvention. To avoid detail not necessary to enable those skilled in theart to practice the invention, the description may omit certaininformation known to those skilled in the art. The following detaileddescription is not to be taken in a limiting sense, and the scope of thepresent invention is defined only by the appended claims.

Referring now to FIGS. 1-3B, a reduced-pressure treatment system 100 fortreating a tissue site, e.g. incision 102, is presented. Thereduced-pressure treatment system 100 is presented in the context of ageneral tissue site that includes an incision 102 and an underminedsubcutaneous tissue site 110, but it will be appreciated that thereduced-pressure treatment system 100 may be used to treat manydifferent types of wounds including open wounds or other tissue sites.The tissue site may be the bodily tissue of any human, animal, or otherorganism, including bone tissue, adipose tissue, muscle tissue, dermaltissue, vascular tissue, connective tissue, cartilage, tendons,ligaments, or any other tissue.

The reduced-pressure treatment system 100 is shown in a peri-incisionalregion around incision 102, which is through epidermis 104, or skin, anddermis 106 and reaching into hypodermis, or subcutaneous tissue 108. Thesubcutaneous tissue 108 may include numerous tissue types such as fattytissue or muscle. An undermined subcutaneous tissue site 110 is shownextending out from incision 102 and includes, in this instance,subcutaneous defect or void 112. The undermined subcutaneous tissue 110is often caused by surgical procedures, such as liposuction. Theundermined subcutaneous tissue 110 may include voids, such as void 112,open spaces, and various defects that can be troublesome for a number ofreasons, such as allowing fluids to build that may result in edema. Theterm “fluid” as used herein generally refers to gas or liquid, but mayalso include any other flowable material, including but not limited togels, colloids, and foams.

The incision 102 may be closed using any mechanical closing means suchas staples, sutures, or adhesive, but is shown in this illustrativeembodiment with a suture 114. The illustrative embodiment shows thereduced-pressure treatment system 100 in use in a peri-incisionalregion. It will be appreciated that the reduced-pressure treatmentsystem 100 may be used to treat undermined subcutaneous tissue 110 wherethere is no corresponding incision or any other kind of tissue site.

The reduced-pressure treatment system 100 generally includes a drape, orwound drape 116, a manifold 120, and a reduced-pressure subsystem 122.The reduced-pressure treatment system 100 may also include grippingmember 118. The wound drape 116 is generally formed from a sheet, orflexible sheet 123, and includes one or more first isotropic zones 124and one or more second isotropic zones 126. Each zone is typically aregion, or area, that makes up at least one half percent of the wounddrape 116. The first and second isotropic zones 124, 126 are configuredto provide the flexible sheet 123 with anisotropic properties. As such,the flexible sheet 123 may help the wound drape 116 primarily stretch ina given direction. Stated another way, the flexible sheet 123 canstretch more along one direction than along another, differentdirection. As used herein, stretching may include elastic and inelasticdeformation. These anisotropic properties may be accomplished in avariety of ways, and several illustrative embodiments will be discussedfurther below beginning with the use of different thicknesses.

In the illustrative embodiment of FIGS. 1-3B, the first isotropic zones124 have a first thickness (t₁) of drape material and the secondisotropic zones 126 have a second thickness (t₂) of drape material, andthe thickness of each first isotropic zone 124 is greater than thethickness of each second isotropic zone 126 (t₁>t₂). Because thethickness (t₁) of each first isotropic zone 124 is greater than thethickness (t₂) of each second isotropic zone 126, the flexible sheet 123is provided with anisotropic properties whereby the flexible sheet 123stretches more in the direction of a first (x) axis 128 than in thedirection of a second (y) axis 130 under equal force in the direction ofeach axis. In one illustrative embodiment, the first thickness (t₁) isgreater than or equal to one hundred five percent (105%) of the secondthickness (t₂), i.e., t₁≧105% t₂. In another illustrative embodiment,the first thickness (t₁) is greater than or equal to one hundred tenpercent (110%) of the second thickness (t₂), i.e., t₁≧110% t₂. Otherrelationships between the first thickness (t₁) and the second thickness(t₂) are possible.

Indeed, by selecting appropriate thicknesses, a user may selectivelycontrol the rate or force with which the flexible sheet 123 attempts toreturn to its original size after it is stretched and adhered to apatient. Thus, the rate of the translation and/or approximation oftissue may be regulated. Regulating the translation and/or approximationof tissue may serve to minimize skin complications, such as blisters,hyper-pigmentation, etc., as well as to assist in closing the incision102. Additionally, the thicker first isotropic zones 124 may be capableof providing a compressive force that may be realized in thesubcutaneous tissue 108 and may be beneficial in treating the underminedsubcutaneous tissue 110 and eliminating voids 112 or the like. As shownin FIG. 2, the first isotropic zones 124 may project inwardly from askin-facing surface 132. As shown in FIG. 3A, the first isotropic zones124 may project outwardly from a first surface 134 of the flexible sheet123. As shown in FIG. 3B, the first isotropic zones 124 may project fromboth of the skin-facing surface 132 and first surface 134. It will beappreciated that any number of isotropic zones may be employed as partof flexible sheet 123. Moreover, while the isotropic zones 124, 126 areshown as substantially parallel with one another, it will be appreciatedthat the zones 124, 126 may be arranged with different orientations withrespect to one another. While two thicknesses (t₁ and t₂) are shown fortwo zones 124, 126, it should be understood that many zones havingvarying thicknesses may be used to achieve the anisotropic properties.

The wound drape 116 may be sized so that it overlaps the incision 102and/or undermined subcutaneous tissue 110 in such a manner that a drapeextension 136 extends beyond the periphery of the incision 102 and/orundermined subcutaneous tissue 110. The wound drape 116 may be formedfrom any suitable material, such as an impermeable or semi-permeableelastomeric material. “Elastomeric” means having the properties of anelastomer and generally refers to a polymeric material that hasrubber-like properties. More specifically, most elastomers haveelongation rates greater than 100% and a significant amount ofresilience. The resilience of a material refers to the material'sability to recover from an elastic deformation. Examples of elastomersmay include, but are not limited to, natural rubbers, polyisoprene,styrene butadiene rubber, chloroprene rubber, polybutadiene, nitrilerubber, butyl rubber, ethylene propylene rubber, ethylene propylenediene monomer, chlorosulfonated polyethylene, polysulfide rubber,polyurethane, EVA film, co-polyester, and silicones. Sealing drapematerials may include a silicone material, 3M Tegaderm® drape material,acrylic drape material such as one available from Avery DennisonCorporation of Pasadena, Calif., or an incise drape material. However,it will be appreciated that the wound drape 116 may be formed from anysuitable material. In addition, the first and second isotropic zones124, 126 may be formed from the same drape material or from differentdrape materials. The isotropic zones 124, 126 may be formed via aco-extrusion process, a molding process, or any other suitable formingprocess. The varying thicknesses may be achieved by coupling two or moreportions of drape material that are not co-extensive. Optionally, thedrape material may also include one or more suitable bioactive elements,including, but not limited to, antimicrobial compounds or any othersuitable bioactive element(s).

The gripping member 118 may be coupled to the wound drape 116. Thegripping member 118 is operable to couple the wound drape 116 to apatient's epidermis 104. Also, the gipping member 118 may also beoperable to transmit a closing force generated by drape 116 as the drape116 attempts to return to the drape's 116 original size after beingstretched and adhered to a patient (the transmitted force is illustratedas force vectors 138 in FIG. 2). Additionally, the wound drape 116 andgripping member 118 work together to form a fluid seal over thepatient's epidermis 104. “Fluid seal,” or “seal,” means a seal adequateto hold reduced pressure at, the desired site given the particularreduced-pressure subsystem involved. The gripping member 118 may be anymaterial suitable for coupling the drape 116 to a patient's epidermis104, transmitting a closing force to the patient's epidermis 104, and/orassist in forming a fluid seal over the patient's epidermis 104. Forexample, the gripping member 118 may be a pressure sensitive adhesive,heat-activated adhesive, sealing tape, double-sided sealing tape, paste,hydrocolloid, hydrogel, hooks, sutures, etc.

In the illustrative embodiment, the gripping member 118 is an adhesivelayer coupled to the skin-facing surface of the drape extension 136;however, it will be appreciated that gripping member 118 may span theentire width of the drape 116. Alternatively, the gripping member 118may be applied to only a selected portion of the wound drape 116, suchas the first or second isotropic zones 124, 126. The gripping member 118may be formed as a layer or a pattern distributed on the wound drape116. Alternatively, in the case of sealing tape, the gripping member 118may be applied over the entire first surface 134 of the wound drape 116or over the first surface of the drape extension 136.

The manifold 120 is positionable between the skin-facing surface 132 ofthe wound drape 116 and the tissue site, e.g., incision 102, within awound bed, or over an intact portion of the epidermis 104. The term“manifold” as used herein generally refers to a substance or structurethat is provided to assist in applying reduced pressure to, deliveringfluids to, or removing fluids from a tissue site, e.g., incision 102.The manifold 120 may be made of many different materials.

In one illustrative embodiment, the manifold 120 is made from a porousand permeable foam-like material and, more particularly, a reticulated,open-cell polyurethane or polyether foam that allows good permeabilityof wound fluids while under a reduced pressure. One such foam materialthat may be used is the V.A.C.® GranuFoam® material available fromKinetic Concepts, Inc. (KCI) of San Antonio, Tex. Any material orcombination of materials may be used for the manifold material providedthat the manifold material is operable to distribute the reducedpressure. The manifold 120 typically includes a plurality of flowchannels or pathways that distribute fluids provided to and removed fromthe area of tissue around the manifold 120. The flow channels may beinterconnected. Examples of manifolds may include, without limitation,devices that have structural elements arranged to form flow channels,cellular foam, such as open-cell foams, textiles, porous tissuecollections, and liquids, gels, and foams that include, or cure toinclude, flow channels. The manifold material may also be a combinationor layering of materials. For example, a first manifold layer ofhydrophilic foam may be disposed adjacent to a second manifold layer ofhydrophobic foam to form the manifold material.

The reticulated pores of the GranuFoam® material, that are in the rangefrom about 400 to 600 microns, are helpful in carrying out the manifoldfunction, but other materials may be used. The manifold material may bea reticulated foam that is later felted to a thickness of about ⅓ of themanifold material's original thickness. Among the many possiblematerials, the following may be used: GranuFoam® material or a Foamex®technical foam (www.foamex.com). In some instances it may be desirableto add ionic silver to the foam in a microbonding process or to addother substances to the manifold material such as antimicrobial agents.The manifold material may be isotropic or anisotropic. In addition, themanifold material may be a bio-absorbable or bio-includable material.

The manifold 120 may be coupled to the wound drape 116. As used herein,the term “coupled” includes coupling via a separate object and includesdirect coupling. The term “coupled” also encompasses two or morecomponents that are continuous with one another by virtue of each of thecomponents being formed from the same piece of material. Also, the term“coupled” may include chemical, such as via a chemical bond, mechanical,thermal, or electrical coupling. Fluid coupling means that fluid is incommunication between the designated parts or locations.

The wound drape 116 and manifold 120 may be coupled using adhesives suchas an acrylic adhesive, silicone adhesive, hydrogel, hydrocolloid, etc.Alternatively, the wound drape 116 and manifold 120 may be bonded byheat bonding, ultrasonic bonding, and radio frequency bonding, etc. Thecoupling may occur in patterns. In addition, structure may be added tothe bond to make the wound drape 116 behave even more anisotropically ina desired direction.

The reduced-pressure subsystem 122 includes a reduced-pressure source140, which can take many different forms. The reduced-pressure source140 provides reduced pressure as a part of the reduced-pressuretreatment system 100. As used herein, “reduced pressure” generallyrefers to a pressure less than the ambient pressure at a tissue sitethat is being subjected to treatment. In most cases, this reducedpressure will be less than the atmospheric pressure at which the patientis located. Alternatively, the reduced pressure may be less than ahydrostatic pressure at the tissue site Reduced pressure may initiallygenerate fluid flow in the manifold 120, a reduced-pressure conduit, orconduit 148, and proximate the tissue site, e.g., incision 102. As thehydrostatic pressure around the tissue site approaches the desiredreduced pressure, the flow may subside, and the reduced pressure may bemaintained. Unless otherwise indicated, values of pressure stated hereinare gauge pressures. The reduced pressure delivered may be static,dynamic (patterned or random) and may be delivered continuously orintermittently. The operable range of reduced pressure may vary widelyas needed, but would typically be between −5 mm Hg and −500 mm Hg.Various sources of reduced pressure may be utilized such as V.A.C.®therapy unit, which is available from Kinetic Concepts, Inc. of SanAntonio, Tex., or a wall suction unit. The reduced-pressure source 140could also be supplied by a portable mechanical means, such as a pistonin a tube, depending on how much leakage there is with the fluid sealbetween the wound drape 123 and the epidermis 104.

In the illustrative embodiment, the reduced-pressure source 140 is shownhaving a battery compartment 142 and a canister region 144 with windows146 providing a visual indication of the level of fluid within canister144. An interposed membrane filter, such as hydrophobic or oleophobicfilter, may be interspersed between reduced-pressure conduit 148 and thereduced-pressure source 140.

The reduced pressure developed by the reduced-pressure source 140 isdelivered through the reduced-pressure conduit 148 to a reduced-pressureinterface 150, or interface 150, which may be an elbow port 152. In oneillustrative embodiment, the elbow port 152 is a TRAC® technology portavailable from Kinetic Concepts, Inc. of San Antonio, Tex. Thereduced-pressure interface 150 allows the reduced pressure to bedelivered to the wound drape 116 and realized within an interior portionof wound drape 116 and the manifold 120. In this illustrativeembodiment, the elbow port 152 extends through the flexible sheet 123 tothe manifold 120, but numerous arrangements are possible.

In operation, the manifold 120 may be placed proximate the tissue site,e.g., incision 102 and/or undermined subcutaneous tissue 110. The wounddrape 116 may be placed over the manifold 120 such that the drapeextension 136 of the wound drape 116 extends beyond the incision 102and/or undermined subcutaneous tissue 110. The drape 116 may bestretched to a desired length. As previously mentioned, while stretchingthe drape 116, the second isotropic zones 126 may stretch more than thefirst isotropic zones 124. The drape extension 136 may then be securedto the patient's epidermis 104 by a gripping member 118 in order to forma fluid seal between the drape 116 and the patient's epidermis 104. Insome instances, the gripping member 118 may also serve to transmit aclosing force to the patient's epidermis 104 generated by the drape 116as the drape 116 attempts to contract while coupled to the patient'sepidermis 104. The reduced-pressure interface 150 is then applied, ifnot already installed, and the reduced-pressure conduit 148 is fluidlycoupled to the reduced-pressure interface 150. The reduced-pressureconduit 148 is also fluidly coupled to the reduced-pressure source 140.The reduced-pressure source 140 may then be activated such that areduced pressure is delivered to the interior of the wound drape 116 andmanifold 120.

As the reduced pressure is delivered, the manifold 120 may compress andcontract laterally to form a semi-rigid substrate. A number ofbeneficial forces and actions may take place. The reduced pressure istransmitted further still through the manifold 120 so that the reducedpressure is experienced at the patient's epidermis 104 and at theincision 102. At least at the early stages of the healing process, thereduced pressure may also be realized through the incision 102 and intothe subcutaneous tissue 108. The reduced pressure helps close defects,such as a subcutaneous void 112, and generally provides stability to thearea. The reduced pressure delivered to the drape 116 also develops acompressive force, as suggested by arrows 154, which again may providestability and therapy. The compressive force, as suggested by arrows154, is more than just at the level of the epidermis 104; thecompressive force may extend down deeper and may be experienced at thelevel of subcutaneous tissue 108.

Further, as the wound drape 116 and manifold 120 laterally contractunder the influence of the reduced pressure, an inward force, assuggested by arrows 156, may develop that helps hold an additionalclosing force on the incision 102 and may generally provide additionalstability to the wound. Thus, the inward force, represented by arrows156, from the reduced pressure and the closing force, represented byarrows 138, generated by the contraction of the drape 116 may acttogether to assist in helping to close the incision 102 and/ormaintaining the incision 102 in a substantially closed position. At thesame time, the reduced pressure delivered to and through the manifold120 helps to remove any exudates and other fluids from the incision 102.All of these actions may improve healing of the tissue site, e.g.,incision 102.

It may be desirable to apply the reduced-pressure treatment system 100in the operating room and allow the system 100 to remain on the patientuntil adequate healing has taken place. In this regard, it may bedesirable to form the wound drape 116, manifold 120, and any otherlayers from transparent materials to allow the healthcare provider togain visual cues about the healing of the tissue site, e.g., incision102, without having to remove the drape 116. Moreover, it should beappreciated that the reduced-pressure treatment system 100 may be usedas a primary wound-closing treatment or as an intermediate step of awound-closing treatment protocol. Furthermore, it will be appreciatedthat the wound drape 116 may be used without,the manifold 120 and/orreduced pressure sub-system 122. Moreover, it should be appreciated thatthe wound-drape 116 may be beneficial as a stand-alone dressing that iscapable of delivering a closing force and/or a compressive force to anincision 102 and/or undermined subcutaneous tissue 110.

Referring to FIGS. 4A and 4B, a second illustrative embodiment of aportion of a reduced-pressure treatment system 200 is shown for treatinga tissue site, such as an incision, undermined subcutaneous tissue, orother wound. The reduced-pressure treatment system 200 is analogous inmost respects to the reduced-pressure treatment system 100 of FIGS. 1-3Band a correlation of parts is generally indicated in this embodiment byindexing the numerals in FIGS. 1-3B by 100. While presented with areduced-pressure interface 250 and conduit 248 for connection to areduced pressure subsystem (not shown), it will be appreciated that thedrape 216 may be used as a stand-alone dressing as well

The wound drape 216 includes a first isotropic zone 224, a secondisotropic:zone 226, and a third isotropic zone 227. The first isotropiczone 224 is thicker than the second isotropic zone 226, and the secondisotropic zone 226 is thicker than the third isotropic zone 227. In thisembodiment, isotropic regions are created so that with equal forceapplied across the drape 216, the region defined by first isotropic zone224 will stretch less than the region defined by second isotropic zone226. It will be appreciated that the isotropic zones 224, 226 227 may beof any suitable thickness relative to one another (e.g., the third zone227 may be the thickest, etc.). Moreover, while the present embodimentshows three isotropic zones, it will be appreciated that any number ofisotropic zones may be employed. The isotropic zones 224, 226, 227 areconcentric with one another and are annular-square shaped areas whenviewed in plan view, However, it will be appreciated that the isotropiczones 224, 226, 227 do not necessarily need to be concentric with oneanother. Additionally, it will be appreciated that each isotropic zone224, 226, 227 may have any suitable shape when viewed in plan, includingbut not limited to circular, elliptical, triangular, rectangular,octagonal, etc.

In another illustrative embodiment, the wound drape 216 has definedisotropic zones 224, 226, 227, but the transitions between zones may begradual. In another illustrative embodiment, the wound drape 216 istapered such that the thickness of the wound drape 216 either graduallyincreases or gradually decreases from an inner portion 270 to the edge272 of the wound drape 216. Thus, the modulus of elasticity of the wounddrape 216 evenly and gadually changes across the length of the wounddrape 216. In FIGS. 4A and 4B, the inner portion 270 is the substantialcenter of the wound drape 216, although the inner portion 270 may belocated anywhere inside the edges 272 of the wound drape 216.

In one example, the wound drape 272 can be thickest at the edge 272 andgradually become thinner towards the inner portion 270 such that thecenter 270 is the thinnest portion of the wound drape 272. The shape ofthe resulting cavity may approximate a cone, including a frustoconicalshape. Conversely, the wound drape 272 can be thinnest at the periphery272 and gradually become thicker towards the center 270 such that thecenter 270 is the thickest portion of the wound drape 272. Any of theillustrative embodiments of the wound drape described herein, includingthose having substantially parallel isotropic zones, are able to haveeven and gradual, or tapered, changes in thickness or elastic modulusinstead of having clearly defined isotropic zones. In an embodiment inwhich the isotropic zones are substantially parallel to one another, theinner portion 270 may extend from one edge of the wound drape 216 to anopposing edge. Tapering of the wound drape 216 can help to relievestrain at a tissue site to which the wound drape 216 is applied, and canalleviate skin irritation (e.g., blisters). Such tapering can also offerdesirable stretching characteristics to facilitate wound healing.

Referring now to FIGS. 5A and 5B, another illustrative embodiment of aportion of a reduced-pressure treatment system 300 for treating a tissuesite on a patient is shown. The reduced-pressure treatment system 300 isgenerally analogous in most respects to that of the reduced-pressuretreatment system 100 of FIGS. 1-3B and a correlation of parts isgenerally indicated in this embodiment by indexing the referencenumerals of FIGS. 1-3B by 200. While presented with a reduced-pressureinterface 350 and conduit 348 for connection to a reduced pressuresubsystem (not shown), it will be appreciated that the wound drape 316may be used as a stand-alone dressing.

The wound drape 316 includes first isotropic zones 324 and secondisotropic zones 326. The first isotropic zones 324 are formed from amaterial having a first modulus of elasticity (λ₁) and the secondisotropic zones 326 are formed from a material having a second modulusof elasticity (λ₂). In the illustrative embodiment, the first modulus ofelasticity is greater than the second modulus of elasticity (λ₁>λ₂) suchthat the second isotropic zones 326 stretch more than the firstisotropic zones 324 when the wound drape 316 is stretched. The wounddrape 316 stretches primarily in one direction versus other directions.For example, in one embodiment, the wound drape 316 may primarilystretch in a direction substantially perpendicular to one or moreelongated isotropic zones 324, 326.

By selecting the appropriate modulus of elasticity for each isotropiczone 324, 326, a user may selectively control the rate or force withwhich the wound drape 316 attempts to return to the drape's 316 originalsize after being stretched and adhered to a patient. Thus, the rate ofor force related to the translation and/or approximation of tissue maybe regulated. While the illustrative embodiment shows two of eachisotropic zones 324, 326, it will be appreciated that any suitablenumber of isotropic zones may be employed. Additionally, it will beappreciated that the wound drape 316 may include any number of isotropiczones of varying moduli of elasticities or even be constructed ofcontinuously variable elasticity across at least one of the wound drapesurfaces. In one embodiment, the isotropic zones nearest the edge of thewound drape 316 have the lowest modulus of elasticity relative to otherisotropic zones of the wound drape 316.

In another embodiment, one or more isotropic zones may have a modulus ofelasticity equal to or substantially similar to that of the tissue at ornear the tissue site to which the zones are attached. As a fewnon-limiting examples, the modulus of elasticity of the isotropic zonemay be within twenty percent of the modulus of elasticity of thepatient's epidermis or within ten percent of the modulus of elasticityof the patient's skin or within five percent of the modulus ofelasticity of the patient's skin. Coordinating the modulus of elasticityof the isotropic zones with the modulus of elasticity of tissue at thetissue site may minimize stress applied to the tissue orstress-shielding and promote healing and minimize scarring. Furthermore,it will be appreciated that the isotropic zones 324, 326 may beconfigured such that they are annular shaped when viewed in plan viewand the isotropic zones 324, 326 may or may not be arranged such thatthe isotropic zones 324, 326 are concentric with one another. Inaddition, while the isotropic zones 324, 326 are shown havingsubstantially similar thicknesses, it will be appreciated that theisotropic zones 324, 326 may be of different thicknesses. Thus, theanisotropicity of the wound drape 316 may be achieved by combiningdifferent zones having different moduli of elasticities as well asdifferent thicknesses. Also, the thickness and moduli of the wound drape316 may evenly and gradually taper along one or more directions of thewound drape 316 or a portion thereof. Moreover, while the isotropiczones 324, 326 are shown as substantially parallel with one another, itwill be appreciated that the isotropic zones 324, 326 may have anysuitable arrangement relative to one another.

Referring now to FIGS. 6A-6B, another illustrative embodiment of aportion of a reduced-pressure treatment system 400 for treating a tissuesite on a patient is shown. The reduced-pressure treatment system 400generally includes a wound drape 416 and one or more gripping members418. A reduced-pressure interface 450 and conduit 448 may be coupled tothe wound drape 416 for connection to a reduced-pressure source (notshown) such that a reduced pressure may be delivered to the tissue site.It should, however, be appreciated that the wound drape 416 may be usedas a stand alone dressing.

The wound drape 416 is generally formed from a flexible sheet 423 havingone or more anisotropic members 457 coupled thereto. The anisotropicmembers 457 are configured to provide the wound drape 416 withanisotropic properties. In this illustrative, non-limiting example, thewound drape 416 is operable to stretch in the areas between theanisotropic members 457, but stretches minimally or not at all in thedirection of the longitudinal axis of the anisotropic members 457. Inthe illustrative embodiment, the anisotropic members 457 comprise aplurality of filaments 458. The filaments 458 may be formed from anysuitable material, including but not limited to, polymer, fabric, metal,composite, elastomer, etc. In addition, the filaments 458 may bearranged such that they are substantially parallel with one another. Itwill, however, be appreciated that the filaments 458 may have anysuitable arrangement capable of providing the drape 416 with anisotropicproperties; for example, the filaments may be in a “thatched”arrangement, a substantially random arrangement, etc. The filaments 458may also be formed from additional drape material in some illustrativeembodiments.

The filaments 458 are coupled to the flexible sheet 423 by any suitablemeans, including but not limited to, adhesive, mechanical fasteners,bonding, sonic welding, etc. The filaments 458 may be coupled to eitherthe skin-facing surface 432 or the first surface 434 of the flexiblesheet 423. Additionally, the filaments 458 may be formed with theflexible sheet 423, through a process such as co-extrusion, whereby thefilaments 458 are substantially co-planar with the flexible sheet 423.Also, while illustrative embodiment shows two anisotropic members 457,it will be appreciated that any number of anisotropic members 457 may beemployed. Further, while the anisotropic members 457 are shown assubstantially parallel with one another, it will be appreciated that theanisotropic members 457 may have any suitable arrangement relative toone another. Moreover, it will be appreciated that the anisotropicmembers 457 may be arranged such that they are annular in shape whenviewed in plan and they may or may not be arranged such that they areconcentric with one another.

While the anisotropic members 457 are shown as comprising a plurality offilaments 458 in this illustrative embodiment, it will be appreciatedthat the anisotropic members 457 may have any suitable configuration andarrangement. For example, the anisotropic members may include adhesivelayers coupled to the flexible sheet 423. The adhesive layers may or maynot be patterned. Other possible configurations and arrangements for theanisotropic members are possible. In addition, the gripping member 418is the same or similar to gripping member 118 of the reduced-pressuretreatment system 100 of FIGS. 1-3B. In the illustrative embodiment, thegripping member 418 may be coupled to the skin-facing surface 432 of theflexible sheet 423. The gripping member 418 may span the entire width ofthe flexible sheet 423 and overlay the filaments 458 or may be locatednear the ends of the flexible sheet 423 as shown in FIG. 6B.

Referring now to FIGS. 7A and 7B, another illustrative embodiment of aportion of a reduced-pressure treatment system 500 for treating a tissuesite on a patient is shown. The reduced-pressure treatment system 500generally includes a wound drape 516 and one or more gripping members518. A reduced-pressure interface 550 and conduit 548 may be coupled tothe wound drape 516 for fluidly coupling to a reduced-pressure source(not shown) such that a reduced pressure may be delivered to the tissuesite. It will, however, be appreciated that the wound drape 516 may beused as a stand alone dressing.

The wound drape 516 is generally formed from a flexible sheet 523 havingone or more fluidly inflatable bladders 560. Each fluidly inflatablebladder 560 includes an interior chamber 562 for receiving a fluid toinflate the fluidly inflatable bladder 560. Fluid is supplied to eachinterior chamber 562 by a corresponding fluid supply tube or conduit564; however, it will be appreciated that a single fluid supply tube maybe configured to deliver fluid to each bladder via passageways (notshown) that interconnect the fluidly inflatable bladders 560. The fluidmay be delivered to the interior chambers 562 from a fluid control means(not shown). The fluid control means may be any suitable device capableof storing and selectively delivering fluid through the tube(s) 564 tothe interior chambers 562. An illustrative fluid control means includes,but is not limited to, a pump, cylinder, reservoir, etc. withcorresponding control mechanisms, including, but not limited to, valves,clamps, regulators, etc. The fluidly inflatable bladders 560 may beinflated with any suitable material, including but not limited to, air,water, saline, a gel, a foam, etc.

The fluidly inflatable bladders 560 are configured to provide the wounddrape 516 with anisotropic properties. In the illustrative embodiment,the fluidly inflatable,bladders 560 provide the wound drape 516 withanisotropic properties by virtue of the rigidity they supply such thatthe wound drape 516 functionally behaves similarly to that of FIG. 1-3Bwhereby the flexible sheet 523 stretches more in the area between thebladders 560 when a stretching force is applied thereto. Furthermore, itwill be appreciated that by controlling the volume of fluid deliveredthrough the fluid supply tubes 564, it may be possible to control theanisotropic properties of the wound drape 516. For example, as the fluidis delivered to the fluidly inflatable bladders 560, the anisotropicityof the drape 516 may increase. The fluid delivered through the tube 564may also be varied to provide a dynamic anisotropic sheet. A controllermay be provided to control the fluid control means in response toconditions at the wound site. Moreover, it will be appreciated thatinflating the fluidly inflatable bladders 560 prior to stretching andapplying the wound drape 516 may further enhance the anisotropicbehavior. In addition, once the fluidly inflatable bladders 560 areinflated, they may be operable to provide a compressive force that maybe realized in subcutaneous tissue and that may be beneficial intreating the undermined subcutaneous tissue and eliminating voids or thelike.

The fluidly inflatable bladders 560 may be coupled to the flexible sheet523 by any suitable means, including but not limited to adhesive,mechanical fasteners, bonding, sonic welding, etc. The fluidlyinflatable bladders 560 may be coupled to either the skin-facing surface532 or first surface 534 of the flexible sheet 523. Additionally, thefluidly inflatable bladders 560 may be formed to be substantiallyco-planar with the flexible sheet 523 prior to their inflation. Whilethe illustrative embodiment shows four fluidly inflatable bladders 560,it will be appreciated that any number of bladders 560 may be employed.Further, while the fluidly inflatable bladders 560 are shown assubstantially parallel with one another, it will be appreciated that thefluidly inflatable bladders 560 may have any suitable arrangementrelative to one another. Moreover, it will be appreciated that thefluidly inflatable bladders 560 may be arranged such that the fluidlyinflatable bladders 560 are annular shaped when viewed in plan and thefluidly inflatable bladders 560 may or may not be arranged such that thefluidly inflatable bladders 560 are concentric with one another.

In addition, the gripping member 518 is the same or similar to thegripping member 118 of the reduced-pressure treatment system 100 ofFIGS. 1-3B. In the illustrative embodiment, the gripping member 518 maybe coupled to the skin-facing surface 532 of the flexible sheet 523. Thegripping member 518 may span the entire width of the flexible sheet 523and overlay the filaments 558 or may be located near the ends of theflexible sheet 523.

In one illustrative embodiment, the fluidly inflatable bladders 560 areinflated with positive pressure through fluid supply tubes 564 and asreduced pressure is supplied to the reduced-pressure interface 550, theinflatable bladders 560 press against the patient's epidermis with acompressive force. As reduced pressure increases, the inflatablebladders 560 are drawn toward the reduced-pressure interface 550 andthereby create a closing force. The closing force is realized at theepidermis and may be realized at deeper levels, e.g., the dermis.

Although the present invention and its advantages have been disclosed inthe context of certain illustrative, non-limiting embodiments, it shouldbe understood that various changes, substitutions, permutations, andalterations can be made without departing from the scope of theinvention as defined by the appended claims. It will be appreciated thatany feature that is described in a connection to any one embodiment mayalso be applicable to any other embodiment.

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 30. A wound drape comprising: a flexible sheet comprising animpermeable or semi-permeable elastomeric material; and an anisotropicmember coupled to the flexible sheet and configured to provide theflexible sheet with anisotropic stretching properties such that theflexible sheet stretches more in a first direction than in a seconddirection.
 31. The wound drape of claim 30 wherein the anisotropicmember comprises a plurality of filaments.
 32. The wound drape of claim30 wherein the anisotropic member comprises a plurality of filaments andwherein said plurality of filaments are substantially parallel to oneanother.
 33. The wound drape of claim 30 wherein the anisotropic memberis an adhesive layer.
 34. A wound drape comprising: a flexible sheetcomprising an impermeable or semi-permeable elastomeric material; and afluidly inflatable bladder coupled to the flexible sheet and configuredto provide the flexible sheet with anisotropic stretching propertiessuch that the flexible sheet stretches more in a first direction than ina second direction.
 35. The wound drape of claim 34 wherein the fluidlyinflatable bladder is substantially co-planar with the flexible sheetwhen uninflated.
 36. The wound drape of claim 34 further comprising: afluid supply tube fluidly coupled at a first end to the bladder; and afluid control means fluidly coupled to a second end of the fluid supplytube, the fluid control means for selectively applying fluid to thebladder.
 37. The wound drape of claim 34 wherein the bladder is capableof providing a compressive force to a patient's tissue.
 38. A wounddrape comprising: a flexible sheet comprising an impermeable orsemi-permeable elastomeric material and having an inner portion and anedge, the thickness of the flexible sheet gradually changes from theinner portion to the edge to provide the flexible sheet with anisotropicstretching properties such that the flexible sheet stretches more in afirst direction than in a second direction.
 39. The wound drape of claim38, wherein the inner portion is the substantial center of the wounddrape.
 40. The wound drape of claim 38, wherein the modulus ofelasticity of the flexible sheet gradually changes from the innerportion to the edge.
 41. The wound drape of claim 38, wherein thethickness of the flexible sheet gradually increases from the innerportion to the edge such that the edge is thicker than the innerportion.
 42. The wound drape of claim 38, wherein the thickness of theflexible sheet gradually decreases from the inner portion to the edgesuch that the edge is thinner than the inner portion.
 43. (canceled) 44.A method of manufacturing a wound drape, the method comprising the stepsof: forming a flexible sheet for placing over a tissue site, theflexible sheet comprising an impermeable or semi-permeable elastomericmaterial and having a first isotropic zone and a second isotropic zone;and wherein the first isotropic zone and the second isotropic zone areconfigured to provide the flexible sheet with anisotropic stretchingproperties.
 45. The method of claim 44 wherein the first isotropic zonehas a first thickness (t₁) and the second isotropic zone has a secondthickness (t₂) and wherein the first thickness is greater than thesecond thickness (t₁>t₂).
 46. The method of claim 44 wherein the firstisotropic zone has a first thickness (t₁) and the second isotropic zonehas a second thickness (t₂) and wherein the first thickness is greaterthan one hundred five percent (105%) of the second thickness (t₁>105%t₂).
 47. The method of claim 44 wherein the first isotropic zonecomprises a first material having a first modulus of elasticity (λ₁);the second isotropic zone comprises a second material having a secondmodulus of elasticity (λ₂); and the first modulus of elasticity isgreater than the second modulus of elasticity (λ₁>λ₂).
 48. The method ofclaim 44 wherein the first isotropic zone is substantially parallel withthe second isotropic zone.
 49. The method of claim 44 wherein the firstisotropic zone is substantially concentric with the second isotropiczone.
 50. The method of claim 44 wherein the first isotropic zonecomprises a fluidly inflatable bladder.